The present invention relates to a vacuum evaporation apparatus for depositing an evaporant as a thin film on a substrate.
There has been proposed a vacuum evaporation apparatus having a bell jar for defining a vacuum chamber, a storage tank for storing a heat medium such as oil heated to a desired temperature, a substrate support in the form of a container for supporting a substrate thereon, and a pump disposed outside of the bell jar for pumping the heated heat medium from the storage tank into the substrate support to heat the substrate therein and from the substrate support back into the storage tank to thereby effect forced circulation of the heat meadium.
The known vacuum evaporation apparatus with forced heat medium circulation requires the heat medium storage tank, the pump for forcibly circulating the heat medium, a piping for the circulation therethrough of the heat medium, and other parts necessary for heat medium circulation, the pump and the piping being heat resistant. Accordingly, the apparatus is costly to construct. Another problem is that since the heat medium is subjected to a heat loss while it is being forcibly circulated, the heat medium cannot heat the substrate uniformly.